/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package java.nio;

import com.google.gwt.corp.compatibility.Endianness;
import com.google.gwt.corp.compatibility.Numbers;

/** HeapByteBuffer, ReadWriteHeapByteBuffer and ReadOnlyHeapByteBuffer compose the implementation of array based byte buffers.
 * <p>
 * HeapByteBuffer implements all the shared readonly methods and is extended by the other two classes.
 * </p>
 * <p>
 * All methods are marked final for runtime performance.
 * </p>
 */
abstract class HeapByteBuffer extends BaseByteBuffer {

	protected final byte[] backingArray;

	protected final int offset;

	HeapByteBuffer (byte[] backingArray) {
		this(backingArray, backingArray.length, 0);
	}

	HeapByteBuffer (int capacity) {
		this(new byte[capacity], capacity, 0);
	}

	HeapByteBuffer (byte[] backingArray, int capacity, int offset) {
		super(capacity);
		this.backingArray = backingArray;
		this.offset = offset;

		if (offset + capacity > backingArray.length) {
			throw new IndexOutOfBoundsException();
		}
	}

	/*
	 * Override ByteBuffer.get(byte[], int, int) to improve performance.
	 * 
	 * (non-Javadoc)
	 * 
	 * @see java.nio.ByteBuffer#get(byte[], int, int)
	 */
	public final ByteBuffer get (byte[] dest, int off, int len) {
		int length = dest.length;
		if (off < 0 || len < 0 || (long)off + (long)len > length) {
			throw new IndexOutOfBoundsException();
		}
		if (len > remaining()) {
			throw new BufferUnderflowException();
		}
		System.arraycopy(backingArray, offset + position, dest, off, len);
		position += len;
		return this;
	}

	public final byte get () {
		if (position == limit) {
			throw new BufferUnderflowException();
		}
		return backingArray[offset + position++];
	}

	public final byte get (int index) {
		if (index < 0 || index >= limit) {
			throw new IndexOutOfBoundsException();
		}
		return backingArray[offset + index];
	}

	public final double getDouble () {
		return Numbers.longBitsToDouble(getLong());
	}

	public final double getDouble (int index) {
		return Numbers.longBitsToDouble(getLong(index));
	}

	public final float getFloat () {
		return Numbers.intBitsToFloat(getInt());
	}

	public final float getFloat (int index) {
		return Numbers.intBitsToFloat(getInt(index));
	}

	public final int getInt () {
		int newPosition = position + 4;
		if (newPosition > limit) {
			throw new BufferUnderflowException();
		}
		int result = loadInt(position);
		position = newPosition;
		return result;
	}

	public final int getInt (int index) {
		if (index < 0 || index + 4 > limit) {
			throw new IndexOutOfBoundsException();
		}
		return loadInt(index);
	}

	public final long getLong () {
		int newPosition = position + 8;
		if (newPosition > limit) {
			throw new BufferUnderflowException();
		}
		long result = loadLong(position);
		position = newPosition;
		return result;
	}

	public final long getLong (int index) {
		if (index < 0 || index + 8 > limit) {
			throw new IndexOutOfBoundsException();
		}
		return loadLong(index);
	}

	public final short getShort () {
		int newPosition = position + 2;
		if (newPosition > limit) {
			throw new BufferUnderflowException();
		}
		short result = loadShort(position);
		position = newPosition;
		return result;
	}

	public final short getShort (int index) {
		if (index < 0 || index + 2 > limit) {
			throw new IndexOutOfBoundsException();
		}
		return loadShort(index);
	}

	public final boolean isDirect () {
		return false;
	}

	protected final int loadInt (int index) {
		int baseOffset = offset + index;
		int bytes = 0;
		if (order == Endianness.BIG_ENDIAN) {
			for (int i = 0; i < 4; i++) {
				bytes = bytes << 8;
				bytes = bytes | (backingArray[baseOffset + i] & 0xFF);
			}
		} else {
			for (int i = 3; i >= 0; i--) {
				bytes = bytes << 8;
				bytes = bytes | (backingArray[baseOffset + i] & 0xFF);
			}
		}
		return bytes;
	}

	protected final long loadLong (int index) {
		int baseOffset = offset + index;
		long bytes = 0;
		if (order == Endianness.BIG_ENDIAN) {
			for (int i = 0; i < 8; i++) {
				bytes = bytes << 8;
				bytes = bytes | (backingArray[baseOffset + i] & 0xFF);
			}
		} else {
			for (int i = 7; i >= 0; i--) {
				bytes = bytes << 8;
				bytes = bytes | (backingArray[baseOffset + i] & 0xFF);
			}
		}
		return bytes;
	}

	protected final short loadShort (int index) {
		int baseOffset = offset + index;
		short bytes = 0;
		if (order == Endianness.BIG_ENDIAN) {
			bytes = (short)(backingArray[baseOffset] << 8);
			bytes |= (backingArray[baseOffset + 1] & 0xFF);
		} else {
			bytes = (short)(backingArray[baseOffset + 1] << 8);
			bytes |= (backingArray[baseOffset] & 0xFF);
		}
		return bytes;
	}

	protected final void store (int index, int value) {
		int baseOffset = offset + index;
		if (order == Endianness.BIG_ENDIAN) {
			for (int i = 3; i >= 0; i--) {
				backingArray[baseOffset + i] = (byte)(value & 0xFF);
				value = value >> 8;
			}
		} else {
			for (int i = 0; i <= 3; i++) {
				backingArray[baseOffset + i] = (byte)(value & 0xFF);
				value = value >> 8;
			}
		}
	}

	protected final void store (int index, long value) {
		int baseOffset = offset + index;
		if (order == Endianness.BIG_ENDIAN) {
			for (int i = 7; i >= 0; i--) {
				backingArray[baseOffset + i] = (byte)(value & 0xFF);
				value = value >> 8;
			}
		} else {
			for (int i = 0; i <= 7; i++) {
				backingArray[baseOffset + i] = (byte)(value & 0xFF);
				value = value >> 8;
			}
		}
	}

	protected final void store (int index, short value) {
		int baseOffset = offset + index;
		if (order == Endianness.BIG_ENDIAN) {
			backingArray[baseOffset] = (byte)((value >> 8) & 0xFF);
			backingArray[baseOffset + 1] = (byte)(value & 0xFF);
		} else {
			backingArray[baseOffset + 1] = (byte)((value >> 8) & 0xFF);
			backingArray[baseOffset] = (byte)(value & 0xFF);
		}
	}
}
